A sound control apparatus for a keyboard-based musical instrument for avoiding a touch of a shutter to a back check, thereby appropriately setting a sound generation timing and maintaining a satisfactory touch feeling. The sound control apparatus comprises a shutter integrated with a hammer adapted to swing associated with a swinging motion of a key, extending along a plane including a path along which said hammer swings, and formed with a cutout in an edge on an opposite side to a direction in which said hammer swings. An optical sensor has a light emitter disposed on one side of the swinging path of said shutter for emitting light, and a light receiver disposed on the other side of the swinging path for receiving the light from said light emitter, and generates a detection signal in accordance with a light receiving state of said light receiver. A CPU sets a sound generation timing at which music sound should be generated based on the detection signal of said optical sensor responsive to opening and closing of a light path of the light from said light emitter of said optical sensor by said shutter, when said hammer swings.